The US military has sent a task force to Jordan to help it handle an influx of Syrian refugees and prepare for other scenarios, including Damascus losing control of its chemical weapons, a senior US defence official said Wednesday.

A 150-strong force of planners and specialists -- led by a senior US officer -- was looking at ways to prevent the increasingly bloody Syrian civil war from spilling across Jordan's borders, said the official, who was attending NATO talks in Brussels and who asked not to be named.

They are based at an outpost north of the capital Amman and just 35 miles (55 kilometers) from the border, making it the closest US military presence to the Syrian conflict.

The United States says it is providing non-lethal aid to the rebels, refraining so far from providing arms because of fears they could end up in the hands of hardline Islamist groups taking part in the struggle.

US President Barack Obama has however warned of a broader intervention should Syria use or lose control of its chemical weapons arsenal